The Coupling Decoupling Network CDN HSS-2 is designed for convenient surge testing with 1.2/50 μs pulses, as defined in IEC/EN 61000-4-5, on unshielded symmetrical high speed telecommunication lines e.g. Ethernet. Coupling modes to 1, 2 or 4 pairs are given and coupled with 40 Ω in series with a capacitive coupling element. The CDN HSS-2 allows testing on ISDN and Ethernet with 10/100BaseT and 1000BaseT as well. Power over Ethernet (PoE) is applicable. With a surge test voltage of 2 kV is the maximal residual voltage at the AE port only 65 V due to the excellent decoupling network. Additional decoupling elements are not required to protect the auxiliary equipment (AE). The high decoupling provides an AE independent pulse shape for the EUT testing. A high measurement reproducibility is given by using the CDN HSS-2. The decoupling network is in accordance to IEC 61000-4-5/Ed.3/77B/674A/CD:2012-05. It can be used with Teseq’s NSG series or any industry standard surge generator with the appropriate connector adapter.